This invention relates to a lubricating oil supplying system for a two cycle engine and more particularly to an improved system for supplying and controlling the amount of lubricant to such engines.
In order to improve the lubrication of engines, particularly those operating on the two cycle principle, and to ensure against the emission of unwanted exhaust gas constituents, various separate lubricating systems have been proposed wherein lubricant is supplied to the engine from a lubricant pump in metered quantities rather than being mixed with the fuel. Such arrangements permit greater control over the amount of lubricant supplied to the engine and thus improve both lubrication and exhaust emission control.
Various ways have been proposed for controlling the amount of lubricant supplied to the engine. One way in which the quantity of lubricant supplied can be controlled is by providing a plunger type pump and varying both the strike and speed of the pump. Such mechanisms are quite complicated and can add to the cost of the system. Another way in which the amount of lubricant supplied is controlled is by employing a positive displacement pump that may or may not have its output stroke varied and a control valve which selectively supplies lubricant from the pump to the engine or returns it back to the return side of the pump. The amount of lubricant supplied is controlled by varying the duty ratio (ratio of supply time to total time of a given cycle).
Although all of the aforedescribed methods can provide good lubricant control, there is a disadvantage with most of the systems previously proposed. That is, then the lubricant supplied to the engine is initiated, this is, done in response to the engine running condition at that timed However, if the engine running condition varies during the control period, then an improper amount of lubricant supply will be supplied. For example, if the lubricant supply period is begun when the engine is running at a high speed and the engine is thereafter decelerated, an excess amount of lubricant will be supplied which will result in excess lubricant in the exhaust gases and poor emission control. On the other hand, if the lubricant supply is initiated when the engine is running at a low speed and the engine is thereafter accelerated during the same control cycle, then inadequate lubrication may be supplied to the engine.
It is, therefore, a principal object of this invention to provide an improved lubricant supply system for an engine and an improved control therefor.
It is a further object of this invention to provide an improved lubricating system for an engine that can cope with changes in running conditions during the control cycle.
Although systems have been proposed that can monitor the engine running conditions and change the supply characteristics during a given supply cycle, the systems which have been proposed are somewhat complicated and expensive. It is, therefore, a still further object of this invention to provide an improved and simplified lubricant control system for an engine that can be responsive to changing conditions and still be relatively low in cost and simple in operation.